As interior illumination systems to which the invention pertains, there are interior illumination systems disclosed in Patent Document 1 and Patent Document 2. As is shown in FIG. 29, an interior illumination system 100 disclosed in Patent Document 1 includes lamp units 101, 102, which are two on-board interior illumination units, a switch unit 103, which is an on-board interior illumination unit interposed between the two lamp units, a wiring harness WH which constitutes a path that is laid to connect at least the two lamp units 101, 102 and the switch unit 103 and an illumination cover 104 which accommodates the two lamp units 101, 102 and the switch unit 103 and which is fixed to a ceiling of a passenger compartment of a vehicle.
As is shown in FIG. 30, each of the lamp units 101, 102 of the interior illumination system disclosed in Patent Document 1 has a function part main body 110 and an electric wire protection cover 111 which is installed on the function part main body 110. The function part main body 110 has a housing 112, a lamp 113 which is detachably provided in this housing 112 and a separate switch 114 which is detachably provided in the housing 112. An electric wire lay-down portion 115 is formed on one surface side of the housing 112. A plurality of press-contact terminals 116 are erected in the electric wire lay-down portion 115. The wiring harness WH is laid down in the electric wire lay-down portion 115, so that individual electric wires w of the wiring harness WH are press contacted to desirable press-contact terminals 116. The separate switch 114 is configured so as to select an illumination turn-on mode and a door mode.
In addition, a pair of locking recess portions 112a is provided on each of left- and right-hand side walls of the housing 12 which are positioned at both ends of the electric wire lay-down portion 115 and in positions which face each other.
The electric wire protection cover 111 has a pair of electric wire bending projecting portions 111a which projects further downwards than a central inner surface. A locking claw 111b is provided individually on both side surfaces of each electric wire bending projecting portion 111a. The electric wire protection cover 111 covers the wiring harness WH laid down in the electric wire lay-down portion 115 from thereabove, and the locking claws 111b are locked individually in the corresponding locking recess portions 112a in the housing 112.
The switch unit 103 includes, as is shown in FIG. 29, a function part main body 120 in which press-contact terminals (not shown) are erected in an electric wire lay-down portion (not shown) and the electric wires w of the wiring harness WH are press contacted to the press-contact terminals, an electric wire protection cover 121 which is installed on the function part main body 120 and which covers the electric wires w which are laid down in the electric wire lay-down portion and a mode changeover switch (not shown) which is provided in the function part main body 120. The mode changeover switch is configured so as to select an illumination turn-off mode and a door mode.
As is shown in FIG. 31, an interior illumination system 130 disclosed in Patent Document 2 includes lamp units 131, 132, 133, which are three on-board interior illumination units, a switch unit, which is an on-board interior illumination unit interposed between the lamp units 131, 132 and a plurality of inter-unit electric wires 135 which connect the three lamp units 131, 132, 133 and the switch unit 134, and the three lamp units 131, 132, 133 and the switch unit 134 are fixed to a ceiling trim 136 of a passenger compartment. The lamp unit 131 is connected to a wiring harness WH which is laid on the side of a vehicle body.
As is shown in detail in FIG. 32, the lamp unit 131 of the second conventional example has a function part main body 140, and this function part main body 140 has a switch portion 141, a lamp installation portion 142 and two connectors 143 (only one of which is shown). A lamp 144 is installed in the lamp installation portion 142. A connector (not shown) on a side of the lamp unit 131 which faces the inter-unit electric wires 135 shown in FIG. 31 is installed in one of the two connectors which is not shown. A connector 145 connected to the wiring harness WH laid down on the vehicle body is installed in a connector 143 shown in FIGS. 31 and 32.